(1) Field of the Invention
This invention relates to separation of leukocytes or lymphocytes from a leukocyte-containing suspension. More particularly, it relates to a material used for separating leukocytes or lymphocytes from a leukocyte-containing suspension, a method of such separation and a filter comprising the material used for such separation.
By the term "leukocyte-containing suspension" used herein is meant blood and other leukocyte-containing body fluids. This term should also be interpreted as including physically, chemically and/or biologically treated blood and other body fluids such as, for example, blood diluted with a physiological solution and erythrocyte agglutinant-(such as dextran or hydroxyethyl-starch)-incorporated blood.
(2) Description of the Prior Art
Due to recent developments in haematology and immunology, blood component transfusions, tests of leukocytes, inspections of surface antigens of leukocytes and measurements of subpopulation ratios of lyphocytes have frequently been performed and results of these inspections have been used to remedy and diagnose various diseases. Moreover, tests to classify and separate sub-sets such as helper T-cells and suppressor T-cells have been made at various hospitals and research institutes
As the conventional method of entrapping and collecting leukocytes or lymphocytes applicable to the foregoing uses, there can be mentioned a method using an erythrocyte-agglutinant, a centrifugal separation method and a method utilizing adhesion of leukocytes or lymphocytes to fibers.
According to the method using an erythrocyte-agglutinant, dextran, hydroxyethyl starch or other erythrocyte-agglutinant is added to blood, the blood is allowed to stand for a certain time and, then, a supernatant rich in leukocytes is recovered. According to the centrifugal separation method, blood is subjected to centrifugal separation and a buffy coat rich in leucocytes is collected, and according to the density gradient centrifugal separation method, blood is superposed on a liquid having a specific gravity of 1.077, the superposed layers are centrifuged and the lymphocyte-containing layer is recovered. As the known method utilizing adhesion of leukocytes or lymphocytes to fibers, there can be mentioned a method causing monocytes and granulocytes to adhere to fibers and recovering the adhering hematocytes by using a physiological saline solution or a phosphoric acid-buffered physiological saline solution, and a method comprising preparing a fraction rich in leukocytes by using a coagulant or a centrifugal separator, introducing the leukocyte-rich fraction into a column packed with fibers of nylon or glass wool, maintaining the fraction at 37.degree. C. for about 30 minutes in the column and finally recovering lymphocytes therefrom.
However, these known methods are not satisfactory in that relatively large quantities of erythrocytes and platelets are contained in the collected leukocyte or lymphocyte fractions. If large quantities of erythrocytes and platelets are contained, large errors are frequently caused during various inspections using leukocytes and lymphocytes, and inspections often become impossible.
More specifically, in the method using an erythrocyte-agglutinant, the number of incorporated erythrocytes is from several to about 15 times as large as the number of leukocytes, and the number of incorporated platelets is scores of times as large as the number of leukocytes. In the centrifugal separation method using a buffy coat, the number of incorporated erythrocytes and platelets is several to about 15 times the number of leukocytes, and in the density gradient centrifugal separation method, the number of incorporated platelets is from several times as large as the number of lymphocytes. In the density gradient centrifugal separation method, the number of erythrocytes can be reduced to less than 1/10 of the number of lymphocytes. However, in the case where the specific gravity is reduced in some of the erythrocytes, as in blood of patients, the number of erythrocytes is often several to about 15 times the number of lymphocytes. Furthermore, since the operation is complicated and a substantially long time is required for completion of separation, the obtained leukocytes are damaged and reduction of the functions of the leukocytes or reduction of the survival ratio of the leukocytes is often observed. In the method utilizing adhesion of hematocytes to fibers, the number of ertythrocytes or platelets is often several to about 15 times the number of lymphocytes or granulocytes.